Notifications to self

[vpratfr]

For conversations.

Ses also https://wp-customerarea.com/fr/support/topic/bloquer-la-notification-envoye-a-lauteur-du-message/#post-177006

[tlartaud]

We should improve the notification box to show all the users for whom the notifications will be sent, and add for each a checkbox allowing the users to select or not which ones should receive it.

Additionally, we should replace the "send notification when the post get published" with a simple AJAX button to let the author send the notification again. Eg: even if the post is already published.